Tool bit for mining operations



April 3, 1956 J. BOWEN 2,740,611

TOOL BIT FOR MINING OPERATIONS Filed Jan. 8, 1952 INVENTOR John L Ban/e17 root arr non Minnie OPERATIGNS John L. Bowen, Morgantown, W. Va; Wayne W. Bowen,

administrator of said Eohn L. Bowen, deceased, assignor to Firth Sterling, inc, Pittsburgh, Pa, a corporation of Pennsylvania Application January 3, 1952, Serial No. 265,381

Claims. ((13. 1255-61) This invention pertains to a new and improved tool bit or boring tool and particularly, to a tool suitable for drilling out the value content of a mine, such as a coal mine, and which may customarily be employed in removing the value content of a mine facing.

It has been an established practice in mines to utilize a boring tool bit which is rotated into a mine facing to drill out holes and facilitate removal of the coal and other material by manual, mechanical and explosive methods. Prior to my present invention, tool bits used for this purpose have had a relatively short effective life, have tended to heat up and lose their temper, to encounter too great a cutting resistance, to have a tendency to move off true center during a drilling operation, and to require frequent sharpening of their cutting edges (until it is necessary to discard them as unsuitable for further use). The problem presented by the use of prior art tool bits has been one of long standing and no one skilled in the art to my knowledge has been able to find a practical solution.

It has thus been an object of my invention to solve the problem presented in this connection;

Another object has been to discover important factors involved in the utilization of a tool bit and to solve the problem involved by providing a practical construction utilizing principles evolved from such discoveries;

A further object has been to devise a new and improved tool bit for mining operations which will have a much greater efiective period of life, which will make a more effective utilization of the power available, and which will provide a maximum efiiciency of cutting action.

These and many other objects of my invention will appear to those skilled in the art from the description of my invention.

In the drawings, figure 1 is a vertical side view in elevation of a tool constructed in accordance with my invention;

Figure 2 is a vertical side edge view taken at right angles to Figure 1;

Figure 3 is a top plan view of the tool of Figure 1;

Figure 4 is a fragmental, vertical perspective view of a back (cutting) face of a blade of the tool of figure l to illustrate the mounting of a cutting tip on the tool; and,

Figures 5, 6 and 7 are fragmental vertical elevations showing cutting blades of my invention provided with difierent inclinations of cutting edges or faces.

A tool of the type here provided is powered through a drive shaft and socket while it is advanced into 'a mine facing. The tool has a shank and at least a pair of transversely-outwardly and longitudinally or upwardly projecting blades which define a central spacing therebetween along a longitudinal axis of the tool. Each blade has a longitudinal, planar mounting (back or front) face to which a cutting tip or element is secured (brazed-on) which with the blade, defines cutting faces and cutting edges.

In prior constructions, it has been customary to locate the entering apex or cutting high point edge or point, radially or transversely inside of a medium or a half-way "ice point along the transverse cutting end of each cutting blade (not beyond the central or medium point of :such blade). Those skilled in the art have heretofore believed that such a construction was necessary on the basis that the cutting apex should be as close as possible to the longitudinal or vertical (rotational axis of the tool shank, if the tool is to have any useful period 'of life. I have made a rather startling discovery that this criterion is totally fallacious and that contrary to such prior teachings, the apex or entering edge should be beyond, or transversely or radially-outside of such medium point of the cutting edges or faces of each blade.

Rotational power is imparted through the axial stem and shank of the tool to its cutting blades, and from the blades to their end cutting faces and edges. Although at first glance, it appears that an inside location of the highest cutting point or apex of each blade will minimize torsional force on the blades and their cutting tips, it does not actually do so, because of other and more important factors.

In the first place, I discovered that if the entry point or apex of each blade is moved to the outside of such medium point, that contrary to expectations, torsional stress and strains are decreased by reason of more potent and important considerations which did not enter into prior determinations. When the blades of a tool are being rotated into a mine face and along a hole therein, I determined that radially-inner portions of each cutting face or edge would move with less resistance than outer portions thereof because of the fact that they lie nearer to the-axis of rotation than the outer portions. From this, I deduced that the greater length portion of the cutting face or edge of each blade should, contrary to previous ideas, be inside the separating line (represented by the apex), that the shorter length portion of the cutting face or edges of each blade should be radially outside or nearer-the outside vertical edge of each blade and thus, that the apex formed between the cutting face or edge portions of each blade should be outside of the medium point. My investigations further disclosed that the entry and advance of the apex requires less power than the shaving-out of the hole by the cutting face or edge portions forming such apex and that therefore, an inside location of such apex was not essential, but actually should be avoided.

Another consideration is the fact that the outer cutting face or edge portion is working against the main body of the material (such as the coal facing), while the inner cutting face or edge portion is working against a central core portion of the material. The resistance to the cutting action of the outer portion as compared to the resistance of the inner portion is greater and thus, the overall power requirements of a drilling operation are greatly increased when the longer cutting blade face portion is on the outside of each cutting blade.

I have found that the rotative movement imparted to a bit will effect a greater translation of power with'an attendant lesser speed of rotation to portions of a cutting blade which are nearest its longitudinal axis of rotation, and with an attendant lesser power and a greater speed of rotation to outer portions of the cutting blade. Thus, it is important to apply the greater cutting load to the inside portion of a cutting blade where the radius is less and greater power is generated and this is true, even where as here contemplated, the apex of the cutting blade is outside of a medium or apex point of such cutting blade that is defined by two cutting portions thereof.

In cutting coal and like materials, the problem of removing a core does not arise, due to the fact that the cutting action of the blades breaks or shattersthe material which is relatively brittle and has little tensile or shear strength. I have also determined that moving the apex to the outside of the median point, transversely of each blade, aids in maintaining the alignment of the hole being drilled. In this connection, I have found that the stability of the cutting action is greatly increased by moving the apex or initial contact point of the cutting blade outwardly of the median line.

By providing the new proposed relationship of the cutting face or edge portions of drill bit blades, I not only make a more effective and etficient use of rotational power generated through the shank of the bit, but cut down frictional heat generated and thus, increase the effective speed at which the bit can be operated, provide a more accurate and controllable drilling operation, lessen the wear and tear on the cutting portions of each blade and thus, increase the life of the tool. Another important factor is that the cutting faces or edges of my bit can be used for a much longer period of time than for a conventional tool, because of their more effective operational positioning.

In the illustrated embodiment of my invention shown in Figures 1 to 4, inclusive, I have shown a tool bit having a rectangular shank l9 over which a drill socket is to be removably fitted by a pin 50 extending through the socket and a transverse bore hole 1% in the shank. The integral tool is enlarged upwardly and outwardly from its shank ll) into a body or cutting head part 11 that is slightly conical in its outer boundary, see Figure l, and has a bifurcated construction that merges into a pair of cutting blade parts 12 and 12. Since the construction of each blade part is the same, I will describe the con struction of the part 12 to avoid repetition. difference is that the one blade 12 faces in an opposite direction with respect to or is twisted oppositely from the standpoint of the other blade 12, see particularly Figure 2. That is, the cutting end portion of the blade 12 may be said to slope hackwardly and that of the blade 12 may be said to slope forwardly. The blades 12 and 12 are opposed in their operating relationships.

The blade 12 slopes backwardly from its front side and has'a pair of ground-off or beveled-off face portions 12a and 125 which slope backwardly to an apex edge 12c which is formed with a substantially planar, longitudinal or vertical back face 12d that constitutes an upper portion of working face a. It will be noted that the inside edge of each blade 12 and 12' defines a substantially cylindrical path during rotation of the bit, see Figure l. The shank 10, the body 11 and the blades 12 are of one-piece, integral construction of a suitable material such as cast steel.

A wear-resistant cutting tip 13 has substantially planar, longitudinal or vertical inside and outside faces 13d and 13e, respectively. The tip 13 is at least slightly inset upon the face 12d of the blade 12 and is brazed thereto to make it an integral part of the blade. The tip 13 may be of hard carbon steel or of a special alloy, depending on the type of material to be cut out or drilled. It

will be noted that the tip 13 has a pair of cutting face or surface portions 13a and 1312 which slope backwardly as a continuation of the surfaces 12a and 12b and form a cutting tip apex 130 as a continuation of the apex 120. It will also be noted from Figures 1 and 4 that an inside longitudinal face 13f of the tip or element 13 forms a separate cutting face or edge portion that defines an apex 13g with an end (lower) of the cutting edge or face portion 13b. I have found that this limits the depth of the shaving action and contributes to the overall efiiciency of the bit, although certain advantages of my construction can still be obtained, even if the face portion 13b is sloped downwardly to the bottom edge of the tip 13 to thus eliminate the vertical face portion or inner longitudinal cutting face 13 It will be noted from Figure 4 that the tip 13 is set in a recess of the blade 12 slightly deeper on its radial or transversely inner side to increase the rake or cutting angle horizontally. As shown in Figure 2, the outward The only "L and upward slant of the flat or planar face 13e makes for easier and better cutting.

As shown in this Figure 4, the outer, longitudinal or vertical edge face (between the lines of edges b and h) of the tip part 13 is positioned almost on a face plane of the working face a of the blade part 12 or 12, such that the edge line b of the tip lies approximately on the same plane as an outer edge line c of the blade part and is only slightly inset thereat, see also Figure 2. On the other hand, the inner longitudinal or vertical edge face 13f of the tip is inset to substantially its full depth within the plane of the operating face a of the blade part, such that its edge line d constitutes a continuation of an edge line e of the blade part.

it will be noted that a transverse parting line f'betwcen the tip 13 and the face a of the blade 12 or 12' extends diagonally across a transverse bottom edge face g of the tip. It is thus apparent that the planar operating face 132 of the tip has a transverse rake or outward slope across the operating face a of the blade part 12or'12, and between its inner and outer edge faces. Also, as shown particularly in Figure 2, the cutting face a of each of the blades 12 and 12 has a rake or slope such that planes 0 such faces intersect each other in the cutting head 11 and slope longitudinally-outwardly or upwardly along the length of each blade with respect to a plane representing a longitudinal or vertical axis of the tool. As a result, the edge h of each tip is an advanced, outer cutting edge for the bit.

It will be noted that each inside face 13d rests and abuts upon the substantially planar face 12d of the blade on which it is mounted. The face 13a. as Well as the face 132 provide a substantially planar cutting face portion that defines a transverse angle with respect to the working face a of the blade. The planar face portion of each tip 13 thus defines a transverse angle with respect to its blade 12 or 12 and particularly, with respect to the cutting face a, below the face portion 12d of the blade on which it is mounted. As shown in Figure 2, the face He of the blade 12 may be considered as a front cutting face and the face 132 of the blade 12 as a back cutting face or vice-versa.

In obtaining the new and improved results of my invention, I find there are a number of important features, but that it is essential to provide either a cutting tip apex or point 13c (or 120) that lies outside of a medium point of the pair of cutting surface or face portions 13a and 13b, or the outside cutting face portion 13a of a shorter extent than the inside cutting face portion 13b. Also, as previously intimated, it is important to terminate the inner, longer, cutting surface or face portion 13b above the bottom edge of the cutting tip 13, so as to define a third, substantially longitudinal or vertical, cutting surface 13 The surface 13b may define an angle of between to 75 with respect to the vertical or longitudinal axis of the bit and thus, with respect to face portion 13;; an angle of about 40 to produces optimum results. Figure 5 shows a 25 angle, Figure 6 shows an optimum angle of 40 to 56, and Figure 7 shows an angle of The angle which the cutting face portion 13a forms with the vertical or longitudinal axis of the bit may be substantially the same as that of the surface 13b. The bit of my present invention, although it violates prior criterium, has been definitely found to produce highly improved results and to have a greatly lengthened 0perative life period.

What I claim is:

1. In an improved boring bit having a shank to fit on a drill socket, a bifurcated cutting head extending longitudinally and transversely from the shank, said cutting head having a pair of spaced-apart longitudinally-outwardly-extending cutting blades of like transverse positioning and length on said head to define a substantially common cylindrical path and depth of cut during rotation of the bit, a cutting end portion on one of said blades sloping backwardly to define a substantially planar back face that slopes backwardly from a plane of a longitudinal axis of the bit, a cutting end portion on the other of said blades sloping forwardly to define a substantially planar front face that slopes forwardly from the plane representing the longitudinal axis of the bit to intersect the plane representing the planar back face of the cutting end portion of said first-mentioned blade, a cutting tip of hardened material secured on the planar face of each of said blades, each of said cutting tips having a pair of substantially transversely-extending cutting face end portions which slope from and longitudinally in the same direction as the cutting end portion of the blade upon which it is secured, an inner one of said cutting face end portions inclining transverssly-outwardly, an outer one of said pair of cutting face end portions inclining transversely-inwardly towards the inner one of said pair of cutting face end portions and meeting it in a longitudinallyoutwardly projecting apex cutting edge, the inner cutting face end portion of each of said cutting tips being of a greater length than the outer cutting face end portion, and each of said apex cutting edges being located outside of a transverse median line of each of said cutting tips.

2. An improved bit as defined in claim 1 wherein each of said tips has an inner longitudinal cutting face portion defining an apex with its inner cutting face end portion, and the inner cutting face end portion of each of said cutting tips defines an angle of between 25 to 75 with respect to its inner longitudinal cutting face portion.

3. In an improved boring bit having a shank to fit on a drill socket, a bifurcated cutting head extending longitudinally and transversely from the shank, said cutting head having a pair of transversely spaced-apart and longitudinally extending cutting blades of like transverse positioning and length on said head to define a substantially common path and depth of cut during rotation of the bit, each of said blades sloping transversely outwardly and longitudinally from said head towards their ends, a cutting end portion on one of said blades sloping backwardly to define a substantially planar back face that slopes backwardly from a plane of a vertical axis of the bit and towards the end of said blade, a cutting end portion on the other of said blades sloping forwardly to define a substantially planar front face that slopes forwardly from the vertical plane representing the axis of the bit and towards the end of said blade, a cutting tip of hardened material secured on the planar face of each of said blades, each of said cutting tips having a pair of substantially transversely-extending cutting face end portions which slope from inner and outer sides thereof to meet in a longitudinally-outer apex cutting edge, and each of said cutting tips having a substantially planar cutting face portion mounted upon the planar face of its blade and defining a transverse angle with respect thereto that diverges transversely-outwardly across the planar face of said blade to provide a cutting rake across said blade.

4. In an improved boring bit having a shank to fit on a drill socket, a bifurcated cutting head extending longitudinally and transversely from the shank, said cutting head having a pair of spaced-apart longitudinally-outwardly-extending cutting blades of like transverse positioning and length on said head to define a substantially common cylindrical path and depth of cut during rotation of the bit, a cutting end portion on one of said blades sloping backwardly to define a. substantially planar back face that slopes backwardly from a plane of a longitudinal axis of the bit, a cutting end portion on the other of said blades sloping forwardly to define a substantially planar front face that slopes forwardly from the plane representing the longitudinal axis of the bit to intersect the plane representing the planar back face of the cutting end portion of said first-mentioned blade, at cutting tip of hardened material secured on the planar face of each ofsaid blades, each of said cutting tips having a pair of substantially transversely-extending cutting face end portions which slope from and longitudinally in the same direction as the cutting end portion of the blade upon which it is secured, an inner one of said cutting face end portions inclining transversely-outwardly, an outer one of said pair of cutting face end portions inclining transversely inwardly towards the inner one of said pair of cutting face end portions and meeting it in a longitudinallyoutwardly projecting apex cutting edge, the inner cutting face end portion of each of said cutting tips being of a greater length than the outer cutting face end portion, each of said apex cutting edges being located outside of a transverse median line of each of said cutting tips, each of said tips being mounted in a recess upon the cutting end portion of its blade and brazed in position thereon, the tip that is mounted on the first-mentioned blade havand a substantially planar back cutting face and the tip that is mounted on the other blade having a substantially planar front cutting face, and said front and back cutting faces of said tips defining a transversely-outward angle with respect to the planar cutting face of the cutting blade on which the tip is mounted.

5. In an improved boring bit having a shank to fit on a drill socket, a bifurcated cutting head extending longitudinally and transversely from the shank, said cutting head having transversely spaced-apart and longitudinallyextending cutting blades of like transverse positioning and length on said head to define a substantially common path and depth of cut during rotation of the bit, a cutting end portion on one of said blades sloping backwardly to define a substantially planar back face that slopes backwardly from a plane of a longitudinal axis of the bit and towards the end of said blade, a cutting end portion on another of said blades sloping forwardly to define a substantially planar front face that slopes forwardly from the longitudinal plane representing the axis of the bit and towards the end of said blade, at cutting tip of hardened material secured on the planar face of each of said blades, and each of said cutting tips having a substantially planar cutting face portion mounted upon the planar face of its blade and defining a transverse angle with respect thereto that diverges transversely-outwardly across the planar face of said blade to provide a cutting rake across said blade.

References Cited in the file of this patent UNITED STATES PATENTS 2,461,305 Winn Feb. 8, 1949 2,614,814 Jones et al. Oct. 21, 1952 FOREIGN PATENTS 130,357 Australia Nov. 30, 1948 416,282 Germany Sept. 13, 1934 547,866 Great Britain Sept. 15, 1942 

